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; Compiled with
; nasm -f elf64 prime.asm && gcc -o prime prime.o
global _start
extern atoi
extern printf
extern puts
section .text
main:
cmp rdi, 2 ;check if it has one argument
jne error1
xor rdi, rdi
mov rdi, rsi; argument
call atoi wrt ..plt
mov r8, rdi
inc r8
xor rdi, rdi
mov r9, 2 ;number to begin
mov r11, 11
checkPrime2: ; check if divisible by 2
xor rdx, rdx
cmp r8, r9
je done
mov rax, r9
mov rcx, 2
div rcx
mov r10, rax
cmp rdx, 0
je notPrime
checkPrime3: ; check if divisible by 3
xor rdx, rdx
mov rax, r9
mov rcx, 3
div rcx
cmp rdx, 0
je notPrime
checkPrime5: ; check if divisibly by 5
xor rdx, rdx
mov rax, r9
mov rcx, 5
div rcx
cmp rdx, 0
je notPrime
checkPrime7: ; check if is divisible by 7
xor rdx, rdx
mov rax, r9
mov rcx, 7
div rcx
cmp rdx, 0
je notPrime
; increase divisor until it reaches half of the given number.
; r11 is the divisor which will be incremented
; in r10 is the actual number divided by two
divisorIncrease:
xor rcx, rcx
mov rax, r9
mov rcx, r11
div rcx
cmp rdx, 0
je notPrime
cmp r11, r10
je printPrime
inc r11
jmp divisorIncrease
printPrime:
mov rdi, output
mov rsi, r9
call printf wrt ..plt
inc r9
cmp r8, r9 ; r8 contains the argument (highest number) +1
je done
jmp checkPrime2
notPrime:
inc r9
cmp r8, r9
je done
jmp checkPrime2
error1:
mov rdi, noArgument
call puts wrt ..plt
done:
ret
section .data
output:
dq "%d", 10, 0
noArgument:
db "Requires exactly one argument (last number to check)", 10, 0
[BITS 16]
org 0x7c00
mov ah, 0x0e
mov al, 'H'
int 0x10
mov al, 'E'
int 0x10
mov al, 'L'
int 0x10
int 0x10
mov al, 'O'
int 0x10
jmp $
times 510 - ($-$$) db 0
dw 0xaa55
Now the next step is to figure out the easiest (least lines of code) way to enable the A20 line, for COMPLETE access to the full 32bit memory space.
My code to test and enable A20 is:Code: [Select]%define KBC_Control 060h ; KBC Control Port
%define KBC_Status 064h ; KBC Status Port
%define KBC_in_buf_full 002h ; Input buffer full
%define KBC_enable_A20 0DFh ; enable A20 command
;-------------------------------------------------------------------------------+
; EnableA20: +
; +
; input: none +
; +
; output: CF A20 is set +
; NC A20 is not set +
; +
; This routine first tests whether A20 is set. If not, it tries to set it using +
; Port 92 (Fast A20). If that fails, it then writes to the keyboard +
; controller to set it. +
; +
; If A20 is enabled the routine returns with CF set, else CF is cleared. +
;-------------------------------------------------------------------------------+
section .text
EnableA20:
push ax
push dx
call TestA20 ; is A20 set?
jc .1 ; yes, exit
in al,092h ; read Port 92h
or al,02h ; Set A20 bit
out 092h,al ; write it - set A20
call TestA20 ; Test A20 again...
jc .1 ; if set, exit
mov ah,KBC_enable_A20
call KBC_GateA20
call TestA20 ; Test A20 again...
.1:
pop ax
pop dx
ret
;-------------------------------------------------------------------------------+
; TestA20: +
; +
; input: none +
; +
; output: CF A20 is set +
; NC A20 is not set +
; +
; This routine test whether A20 is set or not. +
;-------------------------------------------------------------------------------+
section .text
TestA20:
push ds
push es
push ax ; used a few times...
push bx ; likewise....
push si
push di
xor si,si
xor di,di
mov ds,si ; DS:SI points to Int 0 vector
mov ax,0FFFFh
mov es,ax
mov di,010h ; ES:DI points to:
; 0x0000 if A20 not set
; 0x10000 if A20 is set
cli
push word [DS:0] ; save Int 0 vector
lodsw ; ax contains int 0 vector
mov bx,ax ; save in bx
dec ax ; decrement ax
stosw ; and save to ES:DI
xor si,si
xor di,di
lodsw ; read DS:SI again
cmp ax,bx ; if A20 is set, ZF is set
pop word [DS:0] ; restore Int 0 vector
sti
clc
jnz .1 ; if ZF
stc ; then set CF
.1:
pop di
pop si
pop bx
pop ax
pop es
pop ds
ret
;-------------------------------------------------------------------------------+
; KBC_Wait: +
; +
; input: none +
; +
; output: NC = buffer is empty +
; CF = buffer is not empty +
;-------------------------------------------------------------------------------+
section .text
KBC_Wait:
push ax ; save ax
push bx ; save bx
push cx ; save cx
mov bx,5 ; set super-long timeout
xor cx,cx ; cx=0: timeout value
.1:
out 0edh,ax ; I/O delay
in al,KBC_Status ; read 8042 status port
and al,KBC_in_buf_full ; input buffer full flag (D1)
loopnz .1 ; loop until input buffer empty
; or timeout
jz .2 ; success!
dec bx ; are we done yet?
jnz .1 ; keep trying
or al,al ; success on last try?
.2:
clc
jz .3
stc
.3:
pop cx ; restore cx
pop bx ; restore bx
pop ax ; restore ax
ret
;-------------------------------------------------------------------------------+
; KBC_GateA20: +
; +
; input: ah = command to send to KBC +
; +
; output: NC = Command succeeded +
; CF = Command failed +
;-------------------------------------------------------------------------------+
section .text
KBC_GateA20:
pushf ; save interrupt status
cli ; disable ints while using 8042
Call KBC_Wait ; insure 8042 input buffer empty
jc A20_Fail ; ret: 8042 unable to accept cmd
out 0edh,ax ; I/O delay
mov al,0D1h ; 8042 cmd to write output port
out KBC_Status,al ; output cmd to 8042
Call KBC_Wait ; wait for 8042 to accept cmd
jc A20_Fail ; ret: 8042 unable to accept cmd
mov al,ah ; 8042 port data
out KBC_Control,al ; output port data to 8042
Call KBC_Wait ; wait for 8042 to port data
jc A20_Fail
push cx ; save CX
mov cx,14h ;
.DLY:
out 0edh,ax ; Wait for KBC to execute the
loop .DLY ; command. (about 25uS)
pop cx ; restore CX
clc
A20_Fail:
popf ; restore flags
ret
It's not compact, as it contains lots of checks, but if you need to remove all the checks to make it more compact, that should be easy enough. The I/O delays are needed on some systems, as without it your code may be too fast for the KBC controller.
Now the next step is to figure out the easiest (least lines of code) way to enable the A20 line, for COMPLETE access to the full 32bit memory space.
%define KBC_Control 060h ; KBC Control Port
%define KBC_Status 064h ; KBC Status Port
%define KBC_in_buf_full 002h ; Input buffer full
%define KBC_enable_A20 0DFh ; enable A20 command
;-------------------------------------------------------------------------------+
; EnableA20: +
; +
; input: none +
; +
; output: CF A20 is set +
; NC A20 is not set +
; +
; This routine first tests whether A20 is set. If not, it tries to set it using +
; Port 92 (Fast A20). If that fails, it then writes to the keyboard +
; controller to set it. +
; +
; If A20 is enabled the routine returns with CF set, else CF is cleared. +
;-------------------------------------------------------------------------------+
section .text
EnableA20:
push ax
push dx
call TestA20 ; is A20 set?
jc .1 ; yes, exit
in al,092h ; read Port 92h
or al,02h ; Set A20 bit
out 092h,al ; write it - set A20
call TestA20 ; Test A20 again...
jc .1 ; if set, exit
mov ah,KBC_enable_A20
call KBC_GateA20
call TestA20 ; Test A20 again...
.1:
pop ax
pop dx
ret
;-------------------------------------------------------------------------------+
; TestA20: +
; +
; input: none +
; +
; output: CF A20 is set +
; NC A20 is not set +
; +
; This routine test whether A20 is set or not. +
;-------------------------------------------------------------------------------+
section .text
TestA20:
push ds
push es
push ax ; used a few times...
push bx ; likewise....
push si
push di
xor si,si
xor di,di
mov ds,si ; DS:SI points to Int 0 vector
mov ax,0FFFFh
mov es,ax
mov di,010h ; ES:DI points to:
; 0x0000 if A20 not set
; 0x10000 if A20 is set
cli
push word [DS:0] ; save Int 0 vector
lodsw ; ax contains int 0 vector
mov bx,ax ; save in bx
dec ax ; decrement ax
stosw ; and save to ES:DI
xor si,si
xor di,di
lodsw ; read DS:SI again
cmp ax,bx ; if A20 is set, ZF is set
pop word [DS:0] ; restore Int 0 vector
sti
clc
jnz .1 ; if ZF
stc ; then set CF
.1:
pop di
pop si
pop bx
pop ax
pop es
pop ds
ret
;-------------------------------------------------------------------------------+
; KBC_Wait: +
; +
; input: none +
; +
; output: NC = buffer is empty +
; CF = buffer is not empty +
;-------------------------------------------------------------------------------+
section .text
KBC_Wait:
push ax ; save ax
push bx ; save bx
push cx ; save cx
mov bx,5 ; set super-long timeout
xor cx,cx ; cx=0: timeout value
.1:
out 0edh,ax ; I/O delay
in al,KBC_Status ; read 8042 status port
and al,KBC_in_buf_full ; input buffer full flag (D1)
loopnz .1 ; loop until input buffer empty
; or timeout
jz .2 ; success!
dec bx ; are we done yet?
jnz .1 ; keep trying
or al,al ; success on last try?
.2:
clc
jz .3
stc
.3:
pop cx ; restore cx
pop bx ; restore bx
pop ax ; restore ax
ret
;-------------------------------------------------------------------------------+
; KBC_GateA20: +
; +
; input: ah = command to send to KBC +
; +
; output: NC = Command succeeded +
; CF = Command failed +
;-------------------------------------------------------------------------------+
section .text
KBC_GateA20:
pushf ; save interrupt status
cli ; disable ints while using 8042
Call KBC_Wait ; insure 8042 input buffer empty
jc A20_Fail ; ret: 8042 unable to accept cmd
out 0edh,ax ; I/O delay
mov al,0D1h ; 8042 cmd to write output port
out KBC_Status,al ; output cmd to 8042
Call KBC_Wait ; wait for 8042 to accept cmd
jc A20_Fail ; ret: 8042 unable to accept cmd
mov al,ah ; 8042 port data
out KBC_Control,al ; output port data to 8042
Call KBC_Wait ; wait for 8042 to port data
jc A20_Fail
push cx ; save CX
mov cx,14h ;
.DLY:
out 0edh,ax ; Wait for KBC to execute the
loop .DLY ; command. (about 25uS)
pop cx ; restore CX
clc
A20_Fail:
popf ; restore flags
ret